According to the survey of Japan Electronics and Information Technology Industries Association (JEITA), an average television viewing time per day is 4.5 hours. However, it has been found that a television is not viewed continuously during the 4.5 hours due to recent changes in lifestyle.
For example, when viewing the television while preparing to go to work or school in the morning or while having a meal, a screen of the television may not be continuously viewed. Further, when a program that is sufficient by an input from a voice such as a weather forecast is being broadcasted, viewers may not look at the screen, or may have a conversation with another person. Then, a behavior of beginning to view the screen of the television again due to an interesting keyword running in topical news or sports news is frequently done.
That is, as a representative television viewing form, the television is turned on instead of a clock in the morning, and “simultaneous viewing” of listening to a sound of the television while operating a personal computer (PC) at night has recently increased. When “simultaneous viewing” is performed, power is unnecessarily expended in a state in which the screen of the television is turned on. For this reason, a display device in which an imaging device is installed around the television screen, and power save control optimal for a viewing state is executed by performing face detection through the image device and analyzing a user's viewing state has been proposed.